What are some best practices for handling situations where the HTTP_REFERER variable is blocked or not sent by the client's browser or firewall?

When the HTTP_REFERER variable is blocked or not sent by the client's browser or firewall, it can cause issues with tracking user behavior or preventing unauthorized access. To handle this situation, one approach is to use alternative methods such as session variables or cookies to track user navigation or validate requests.

// Check if HTTP_REFERER is not set or empty
if (!isset($_SERVER['HTTP_REFERER']) || empty($_SERVER['HTTP_REFERER'])) {
    // Use session variables or cookies to track user behavior
    $_SESSION['last_page'] = $_SERVER['REQUEST_URI'];
    // Redirect to a default page or perform other actions
    header('Location: default_page.php');
    exit;
}